Colon Flashcards
According to Duffy 2020 in Vet Surg, which of the following closure techniques was associated with the highest leak pressure following typhlectomy:
1) SCP with Parker-Kerr
2) Stapled
3) Stapled and Cushing’s oversew
Stapled and Cushing’s oversew
In a study by Sapora 2021 in Vet Surg, were stapled or hand sutured large intestinal anastomoses associated with increased leakage pressures? Which closure technique was deemed unsafe for use based on low leakage pressures?
Hand sutured (either using glycomer or barbed glycomer, compared to a 4.8mm and 3.5mm EEA).
The 3.5mm EEA was deemed unsafe for use due to low leakage pressures.
In a study by Matz 2022 in Vet Surg, which of the following TA stapler sizes resulted in the highest initial leak pressures?
1) TA V3 30 2.5mm
2) TA 60 3.5mm
3) TA 60 4.8mm
No difference between staple sizes. All leaked in excess of physiologic pressures.
In a study by Latimer 2019 in JAVMA, what was the post-operative dehiscence rate following full-thickness large intestinal incision in dogs? What were 4 risk factors for mortality, and 6 factors for dehiscence?
Dehiscence rate of 10% (mortality rate of 17%).
Factors for mortality included pre-operative antimicrobials, degenerative neutrophils, preoperative anorexia, hypoglycemia.
Factors for dehiscence included blood tranfusions, preexisting colon trauma or dehiscence, preexisting peritonitis, administration of >2 classes of antibiotic, positive culture result of a surgical sample, open abdominal management of peritonitis.
In a study by Grossman 2021 in JAVMA, what was the major complication rate in cats undergoing subtotal colectomy? What were 4 negative prognostic indicators identified? What was the rate of constipation recurrence? What 2 post-operative outcomes were removal of the ICJ associated with?
Major complication rate of 10%.
4 negative prognostic indicators included preexisting cardiac disease, post-operative liquid feces, body condition score <4/9, major perioperative complications.
Rate of constipation was 32% (not affected by ICJ removal).
Removal of the ICJ was associated with long term liquid feces and a fair or poor outcome on owner assessment.
In a study by Lux 2021 in JAVMA, what was the post-operative dehiscence rate following full-thickness large intestinal incision in cats? What were 3 risk factors for mortality, and 5 factors for dehiscence?
Dehiscence rate of 8% (mortality rate 6%).
Factors associated with nonsurvival to discharge include low serum globulin, repair of colonic trauma/dehiscence, postoperative colonic dehiscence.
Factors associated with dehiscence include hypoalbuminemia, renal dysfunction, administration of blood products, >2 classes of antimicrobials, and intra-abdominal fecal contamination.
In a study by Stecyk 2022 in JAVMA, what percentage of dogs and cats were reported to have a good outcome following ICJ resection? What were 3 common long term issues as reported by owners?
Dogs: 50%, Cats: 73%.
Patients were commonly reported to have diarrhea, weight loss, and muscle loss.
What is the reason for suspected efficacy of tyrosine kinase inhibitors (toceranib, imitanib, mastinib) in GIST?
GIST express c-kit (CD117), a tyrosine kinase (TK) receptor encoded by the proto-oncogene KIT. By targeting this receptor overexpression, tumour growth can be retarded.
What is the difference between the ceocolic orifice in dogs and cats?
Dogs: 1cm distal to the ileocolic orifice.
Cats: adjacent to the ileocolic orifice.
What is the point of origin of the mesocolon?
The ileoceocolic junction. It is very short at this location, tightly tethering the ascending colon. The ascending colon is also limited in movement by its attachments to the mesoduodenum.
Which two structures does the duodenocolic ligament connect?
The ascending duodenum to the descending colon.
Describe the arterial supply to the colon.
What are the two arterial networks of the colon?
Subserosal and mural (largely within the submucosa).
Where do afferent colonic lymphatics drain?
Right, middle and left colic lymph nodes.
What is the autonomic innervation of the colon?
Cranial and caudal mesenteric plexuses.
What are the layers of the colon?
Mucosa, submucosa, muscularis, serosal.
What are the differences between the mucosa of the colon and small intestine?
In the colon the epithelial cells are arranged in parallel crypts and there are no villi or Peyer’s patches, instead there are large solitary lymphoglandular complexes within the mucosa (~3mm in diameter). These lymph complexes are only found in the cecum of the cat.
What are the functions of the colon?
Storing fecal material (primarily the distal colon), reservoir of the colon’s complex microbial ecosystem, and maintaining fluid and electrolyte balance (proximal colon).
The colonic mucosa resorbs water, sodium and chloride, and secretes potassium, bicarbonate and mucus. Disruptions to this balance can result in diarrhea or constipation.
What is the byproduct of bacterial fermentation of dietary fiber in the colon?
Short chain fatty acids. Have a trophic effect on the epithelium, maintain colonic luminal pH, and help prevent colonic irritation.
Feeding diets with nonfermentable fiber leads to a reduction in short chain fatty acids and constipation.
What are the stages of healing in the colon?
Lag phase: typically lasts 72-96 hours. Predominant cell type is the neutrophil and there is minimal wound strength.
Proliferative phase: days 3 and 4 to 14. Fibroblasts proliferate. Type III collagen is increased to 30-40% (remainder being type I). Angiogenesis occurs. Wound bursting strength near normal by day 10-17.
Maturation phase: day 17 onward. Macrophages and fibroblasts dwindle, collagen reorganizes, type III collagen decreases.
What is the normal composition of collagen in the submucosa of the colon?
Type I: 68%
Type III: 20%
Type V: 12%.
How long does epithelial migration take to create a seal in colonic wounds with mucosal apposition ?
3 days
Where is collagen produced in the colon?
Submucosa and smooth muscle cells.
What is colonic wound strength as a percentage of normal strength at 48 hours after injury?
30%. This increases to 75% by 4 months post-operative (although colonic wound strength is ‘near normal’ by 10-17 days following injury).
What are some local and systemic factors that might be detrimental to colonic healing?
Below what partial pressure of oxygen does collagen formation not occur?
40 mmHg.
Below 10 mmHg angiogenesis and epithelial hyperplasia will not occur and wound failure will occur.
Does anemia as low as 15% affect colonic healing?
No, although administration of a blood transfusion might impact healing due to impaired macrophage function.
How can perfusion at the wound edges of the colon be assessed?
Subjective assessment of color, objective use of Doppler ultrasonography and laser Doppler flowmetry.
What are some methods for improving colonic wound healing?
Omentalization, colonic reinforcement (porcine SIS, although concerns over the potential for contraction and stricture exist), cytokines (application of exogenous factors may accelerate angiogenesis, i.e. VEGF).
What suture closure pattern is recommended for the colon?
Single layer, simple interrupted appositional. Monofilament absorbable preferred (doxycycline coating might improve strength of anastomosis by inhibiting MMPs).
What are some options for stapled closure of the colon?
FEESA, triangulating end-to-end anastomosis using TA 30 staplers, EEA device. Use of skin staplers for the large intestine has not been described clinically.
Biofragmentable anastomosis ring has also been described (composed of polyglycolic acid [Dexon] and barium sulfate). High initial bursting strength maintained for 28-days. Complications include serosal tearing, anemia and anorexia.
What are some sutureless closure techniques described for the colon?
Laser (gallium arsenide), tissue glue (cyanoacrylate), fibrin sealant.
Tissue glues have had mixed results and cannot be recommended clinically at this time.
What are some imaging techniques used for evaluation of the colon?
Radiography +/- positive or double contrast, ultrasound (limited utility due to gas), CT/MRI, endoscopy.
What laxative is used for colonoscopy preparation?
Polyethylene glycol with electrolytes, followed by two warm water enemas on the day of the procedure.
Which antimicrobials are recommended for colonic surgery prophylaxis?
Cefoxitin (good action against coliforms and anaerobes). Alternatively cefazolin and metronidazole can be used.
Is mechanical preparation of the bowel recommended prior to colonic surgery?
May be contraindicated as likely to turn fecal material into a liquid slurry.
Why should lidocaine not be administered intravenously in cats?
Due to cardiovascular depression.
Why is the use of epidural anesthesia controversial in colonic surgery?
May alter myoelectrical impulses and cause uncoordinated contractions which could result in intussusception. IV ketamine might be a viable alternative.
How long does transdermal fentanyl take to reach effective concentrations?
24 hours in the dog, 7 hours in the cat.
What diet is recommended following colonic surgery?
High residue (highly fermentable leading to production of short chain fatty acids), low fat diet to promote normal motility.
Fiber promotes the propulsive effects of the colon, whereas fat induces delayed transit time.
How can typhlectomy be performed?
Transection of the ileocecal fold with preservation of the antimesenteric vessels of the ileum followed by clamping, transection and suturing (Parker-Kerr), or stapling with GIA or TA stapler +/- oversew with Lembert.
What suture pattern is shown?
How is the junction between colon and rectum defined?
Debated, but may be considered 1-2 cm cranial to the pelvic brim, 1cm caudal to the site where the caudal mesenteric artery penetrates the serosa.
Are the individual vasa recta or main blood vessels themselves (left, middle, right colic, ileocolic) preferably ligated when performing colectomy?
Individual vasa recta to preserve as much vascular supply to the colon as possible.
When performing subtotal colectomy what is the proximal limit of transection?
Either 1-2 cm distal to the ileocolic junction, or 1-2 cm proximal to the ileocolic fold.
What device is depicted for use during EEA stapling of the colon?
Furniss purse string device
What are two methods of passage of an EEA device into the colon?
Via the rectum or cecum. Transcecal approach is preferred in cats as it does not result in strictures.
Describe the approach for EEA stapling of the colon.
What size EEA cartridge is typically used in cats?
25- or 21-mm device
What are the two techniques described for colostomy? Are they reversible?
End-on colostomy, loop colostomy.
Loop colostomy is reversible by simple resection of the mucocuntaneous junction and closure of the stoma.
End-on colostomy is only reversible if the distal colonic stump is preserved.
What can be performed to reduce fecal output in patients with colostomies?
Warm water enemas once daily.
What are some potential complications after combined abdominal transanal pull-through procedure?
Wound dehiscence, peritonitis, fecal incontinence. The extent of resection is limited by tension on the colonic vascular pedicles.
When might a combined abdominal transanal pull-through procedure be used for tumour removal?
For tumours of the descending colon extending into the cranial or middle third of the rectum.
The colon should be divided 5cm or more cranial to the tumour to ensure adequate resection. Care must be taken to ensure adequate colonic mobility.
How much of the distal rectum is ideally preserved when performing combined abdominal transanal pull-through procedure?
1 - 1.5 cm.
What are the two methods for colonpexy?
Simple appositional (engaging submucosa of the colon) or incisional.
What are the typical clinical signs of a patient with cecal inversion?
Often non-specific GI signs. Can be acute with signs of obstruction and endotoxic shock, or chronic with ongoing diarrhea.
Typically in animals <4 years of age.
Positive contrast radiography, ultrasound and colonoscopy useful for diagnosis.
What is the treatment for cecal inversion?
Colotomy and typhlectomy.
What is the treatment for cecal impaction?
Typhlectomy + biopsies to assess for underlying motility disorder.
What are the most common type of cecal tumours in dogs?
Stromal tumours, although adenocarcinoma also reported. GISTs may be more likely to perforate than leiomyosarcomas.
What is the MST for smooth mucles tumours of the cecum?
681 days. Prognosis does not seem to be related to histologic appearance or immunohistochemistry characteristics.
What paraneoplastic condition might be seen with cecal leiomyosarcoma?
Erythrocytosis secondary to ectopic production of plasma erythropoietin.
What is megacolon?
End stage obstipation characterized by colonic hypomotility and permanent increase in colonic diameter.
What are some causes of megacolon in dogs and cats?
How much narrowing of the pelvic canal typically results in obstructive (hypertrophic) megacolon in cats?
45%
How soon following initial pelvic trauma should surgical correction of pelvic canal narrowing be corrected to prevent permanent megacolon in cats?
6 months.
What are the two main types of megacolon?
Primary (or idiopathic), secondary or (acquired). Secondary obstructive megacolon often referred to as hypertrophic.
What percentage of feline megacolon is idiopathic?
62%. Pelvic stenosis next most common cause (23%).
Most commonly reported in middle aged male cats.
What is the proposed etiology of feline idiopathic megacolon?
Generalized dysfunction of the longitudinal and circular smooth muscle secondary to dysfunction in activation of the smooth muscle myofilaments.
What parameter is used to confirm the presence of megacolon on radiographs?
Colonic diameter 1.5 x the length of L7.
Why should phopshate enemas never be used in cats?
They cause rapid dehydration, hypocalcemia, hypophosphatemia, and death.
Describe an algorithm for diagnosis of primary versus secondary megacolon.
Describe an algorithm for management of primary (idiopathic) megacolon.
What tests should be a part of the work-up of suspected idiopathic feline megacolon?
- Physical and rectal examination.
- Neurologic examination
- CBC, biochemistry and urinalysis (assess for causes of dehydration, electrolyte abnormalities, underlying endocrine disease).
- Radiography +/- ultrasonography
What are medical management options for feline idiopathic megacolon?
Generally ineffective due to chronic and irreversible disease at the time of diagnosis.
Involves correction of electrolyte abnormalities (particularly hypokalemia), manual removal of fecoliths, high-fiber diets, stool softeners, periodic enemas, cisapride.
How does lactulose act as a laxative?
Metabolized by colonic bacteria resulting in the formation of low-molecular weight organic acids. These acids increase osmotic pressure, drawing water into the bowel.
Why is mineral oil not recommended as a laxative?
High risk of aspiration, can lead to malabsorption of fat, and tends to flow around fecoliths.
What is the action of cisapride in the colon?
Release of aceytlcholine from the enteric nervous system, stimulating contraction of smooth muscle in the colon.
Describe a treatment algorithm for seconday megacolon.
Is removal or preservation of the ICJ preferred in subtotal colectomy?
Preservation is preferred as removal results in SIBO, while retention does not increase the risk for recurrent constipation.
May require removal if mobility of the proximal segment is inadequate.
How long does enteric motility take to reestablish following subtotal colectomy?
How does the SI adapt to subtotal colectomy?
8 weeks. Loose stools are expected during this time due to decreased absorptive capacity and transit time.
Increased villous height, enterocyte number and density.
What are some potential complications associated with subtotal colectomy?
Recurrence of constipation (uncommon), incontinence and persistent diarrhea (more common with removal of the ICJ), stricture.
What is the most common signalment of patients affected by colonic volvulus?
Young to middle aged medium to large breed dogs.
In instances of colonic volvulus, which segments of the bowel are affected?
Isolated case reports of volvulus of the left colic and caudal mesenteric vessels without involvement of the ICJ. If the ICJ is involved the cranial mesenteric artery often becomes implicated resulting in diffuse distension of the SI and colon.
What is the most common type of colonic neoplasia in dogs?
Adenocarcinoma, lymphosarcoma and stromal tumours are less frequently reported.
What is the most common type of colonic neoplasia in cats?
Lymphoma and adenocarcinoma.
What are the recommended margins for colonic neoplastic disease?
5-8 cm
What is the MST for dogs with colorectal adenocarcinoma?
6-22 months
What is the metastatic rate of feline colonic neoplasia?
High. ~80% for adenocarcinoma, lymphoma, and mast cell tumours.
What is the MST for cats with colonic adenocarcinoma?
138 days, chemotherapy increased survival to 280 days, but metastatic disease decreased survival to 49 days.
What is the MST for cats with colonic lymphoma?
97 days. Not affected by extent of resection of chemotherapy.
Is surgical removal of colonic duplication recommended?
Yes, as they can undergo malignant transformation.
